In some tool machines there exists the demand that its adjusting and/or feed movements are to be able to be carried out both manually and also by a motor. The handwheel is generally only drivingly coupled when it is operated; it is uncoupled for safety reasons during a motor-driven operation of the spindle or feed screw.
During the manual phase of operation, it is necessary to overcome, aside from the unavoidable feed forces which act onto the threaded spindle, also yet the mass forces of the motor drive which is connected to the threaded spindle. The drive motor itself with its relatively large flywheel mass hingers very considerably a precise adjustment.
It is therefore the purpose of the invention to provide a drive mechanism for a threaded spindle wherein the motor drive is uncoupled from the threaded spindle during the manual operation phase in a simple manner which prevents the occurrence of operating errors.
This purpose is inventively attained by providing a threaded spindle which can be driven both by a drive motor and also by a handwheel, and can become coupled by an axial movement of a control rod on which the handwheel is mounted. The drive connection between the drive motor and the threaded spindle is released through an axial movement of the handwheel so that the output shaft on the motor, on the one hand, is not moved in response to a rotational movement of the handwheel and, on the other hand, cannot drive the threaded spindle in the case of an unintended start.
The coupling mechanism between the drive motor and threaded spindle is generally engaged, namely, these two structural elements are operatively connected. At the same time, the handwheel is uncoupled. In this operating condition, the machine is adjusted for motor feed drive, as it exists for example in the case of a controlled operation.
If the operator engages the handwheel through an axial movement of the handwheel shaft, the motor drive is then automatically uncoupled so that during a manual operation the output shaft thereof does not need to be moved along. An erroneous running along of the handwheel during motor operation is not possible.
The coupling mechanism, which during engagement of the handwheel effects an uncoupling of the motor drive, can be realized in different ways. It can, for example, be mechanical, electro-mechanical, electro-pneumatical or the like.
In a preferred embodiment of the invention, the coupling mechanism is connected to the handwheel through a mechanical linkage or the like. Such a construction is structurally very simple and inexpensive and assures a particularly high safety against breakdown.
It is thereby inventively provided that the drive motor and the coupling mechanism are arranged at one end of the threaded spindle, the handwheel at the other end of the threaded spindle, so that both drives do not hinder one another structurally. Both drives are each capable of becoming drivingly connected to one of the ends of the threaded spindle so that both in the case of a manual and also in the case of a motor operation, the shortest possible power paths and thus small elastic variations exist. The handwheel is, for example, connected to a control rod which is arranged parallel to the threaded spindle and is supported for longitudinal movement, and which control rod in turn is operatively connected to the coupling mechanism between the drive motor and the threaded spindle.
In a different embodiment, it is provided that the coupling mechanism between the drive motor and the threaded spindle is operated through a servodrive controlled through a control switch or the like connected directly or indirectly to the handwheel. Such a construction offers mainly advantages when for space reasons a purely mechanical operating mechanism is not, or only with difficulties, possible. The servodrive can be, for example, an electromagnetic, a hydraulic or pneumatic drive.
Several exemplary embodiments of the invention are illustrated in the accompanying drawings and are described in greater detail hereinafter.